On 04/27/2017 07:35 PM, Andres Freund wrote:
On 2017-04-27 10:29:48 -0700, Joshua D. Drake wrote:
On 04/27/2017 09:34 AM, Andres Freund wrote:
On 2017-04-27 09:31:34 -0700, Joshua D. Drake wrote:
On 04/27/2017 08:59 AM, Andres Freund wrote:
I would agree it isn't yet a widespread issue.
I'm not yet sure about that actually. I suspect a large
percentage of people with such workloads aren't lingering lots on
the lists.
That would probably be true. I was thinking of it more as the
"most new users are in the cloud" and the "cloud" is going to be
rare that a cloud user is going to be able to hit that level of
writes. (at least not without spending LOTS of money)
You can get pretty decent NVMe SSD drives on serveral cloud
providers these days, without immediately bancrupting you. Sure, it's
instance storage, but with a decent replication and archival setup,
that's not necessarily an issue.
It's not that hard to get to the point where postgres can't keep up
with storage, at least for some workloads.
I can confirm this observation. I bought the Intel 750 NVMe SSD last
year, the device has 1GB DDR3 cache on it (power-loss protected), can do
~1GB/s of sustained O_DIRECT sequential writes. But when running
pgbench, I can't push more than ~300MB/s of WAL to it, no matter what I
do because of WALWriteLock.
regards
--
Tomas Vondra http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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